var argvArr = process.argv;
var num = argvArr[2];
if ((typeof num) == "undefined") {
    console.log("please input arg!");
} else if (num == "--help" || num == "-h") {
    console.log("program --help");
}
var result = eval(num);
if (!isNaN(parseInt(result))) {
    console.log(num + "=" + result);
}